So far, large containers having a volume of the order of 3 gallons (about 12 liters) or 5 gallons (about 20 liters) have been adopted worldwide, for example, as refillable bottles for mineral water. Such large containers are generally formed of a resin material and, if empty, they are lightweight and relatively easy to carry. If they are filled with mineral water, however, the containers are considerably heavy and difficult to carry. Thus, in order to make large containers easy to carry, some of them are provided with a handle, which extends along the axial direction (vertical direction) of the trunk, on the outer periphery of the container body (plastic bottle).
By mounting such a handle on the container body, it becomes easy to carry the large container. However, the problem exists that the mounting strength of the handle on the container body cannot be sufficiently enhanced. For example, polycarbonate resin is generally used as a material for a large container. In recent years, however, polyethylene terephthalate (PET) resin has come to be used, and even the use of PET resin as a material for a large container poses the above-mentioned problem. For example, a large container, such as a refillable bottle for mineral water, is normally recovered from a consumer after use, washed with a cleaning fluid at a temperature of the order of 65° C. (hot water washing), and recycled a plurality of times. When PET resin is used as a material for the container body, therefore, it is necessary to mount a handle on the container body firmly while imparting heat resistance to the container body. However, it has been difficult to firmly mount the handle onto the container body while imparting heat resistance to the container body.
To solve such problems, a proposal has been made for an apparatus adapted to push a handle into the body of a mold with a predetermined timing when forming a handle-equipped large container. For example, there is an apparatus equipped with a blow mold (mold body) and a handle insertion device, and configured to insert a handle into the blow mold by the handle insertion device while a preform is being stretched and expanded by an air blow (see Patent Document 1).